May 24, 2015

PLC Logic Auto-Filling Tank - Free PLC Programming

PLC Logic Auto-Filling Tank - Free PLC Programming Almost in all of the industries Tanks are there for storing up the liquid,chemicals or there are overhead water tank for the water supply in plant.Generally for overhead tank a pump is there for filling of the tank or in other cases also there is a motor/pump for filling purpose of tank. So if the filling of tank is a manual process then a operator has to be employed for the ON and OFF process of the PUMP.

PLC Logic for Auto-Filling of Tank - Free PLC Programming

So, as told above if the process of filling is manual then we have to assign this task to a operator to ON the pump when the Tank empties and OFF the pump when the Tank fills. But in today's scenario all the process are automatic. So today we will discuss the automatic filling of tank and automatic ON-OFF of pump according to tank level. We will build a PLC Logic for this complete application. To write the PLC Program for this process we should understand the logic first.

The PLC Logic will be like following

To monitor the level in tank we can either use a Ultrasonic/Capacitive level sensor which will give analog input to PLC OR we can just put two sensor one at HIGH level and another at LOW level and they will give the signal to PLC for HIGH and LOW level respectively.

When the level will be LOW in tank then the PUMP will start and the filling of tank will start and when the level reaches the HIGH level the PLC will receive the HIGH level signal and the PUMP will stop, so the filling of tank will stop. When again tank empties the PUMP will start on its own and the process continues.

Generally the On and OFF of pump at two levels is a task that requires little intelligence. Suppose the height of tank is 5000cm then the low level should be around 2000cm and high level at 4600 cm. It is done because if for example the low level is set at 300cm hen the PUMP will start at 300 cm and suppose if at the same time the consumption rate increases than the supply of PUMP then the tank will empty. So keep in mind this thing while setting the LOW and HIGH level in Tank.

Well there is no need to install a separate PLC for this small application, as almost all the major industries have the PLC installed so the logic can be built in that existing PLC and thus there will be savings.

PLC Logic Development

Here we will take example of Omron PLC and build the PLC logic using CX-Programmer.

0.0-------------------------------------------------------------- Low level Signal
0.1-------------------------------------------------------------- High Level Signal

100.0 ------------------------------------------------------------ PUMP ON

Here we have build the PLC Programming using the digital Inputs, but the same can using the Ultrasonic/Capacitive Level sensor and taking the Analog input to PLC. You can download the PLC program from Below.

Download PLC Programming logic of Auto Filling Tank.

We have attached both .pdf and .cxp files so that who don't have CX-Programmer software can still view the logic and understand the PLC Logic.

We will also build the PLC logic using the Analog input to PLC, so keep visiting and you can subscribe to Automation Talk for such more PLC Programming examples, SCADA tutorials, VFD applications and HMI Programming.

If you have any doubts regarding this PLC Program then you can write in the comment section below and we will get back to you ASAP. Don't forget to Subscribe to Automation-Talk by Email.

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  1. Using only two simple sensor we can identify whether tank is Full or empty then what is the need of PLC ( a high cost device ) ?

  2. PLC has many benefits. It depends whether you want simple sensor or PLC.

  3. Tank Level Control

    I-1 – Start / Stop the process .
    I-2 – Low Level indication switch.
    I-3 – High Level indication switch.

    Q-1 – Inlet Valve ON / OFF
    Q-2 – Outlet Valve ON / OFF
    Q-3 – Stirrer ON / OFF

    When Start switch is ON, check tank level.
    If Low Level is ON, Make Inlet Valve Q1 ON.
    When High Level is reached, Make Inlet Valve Q1 OFF.

    Once High Level is reached and Inlet Valve has become OFF, make Stirrer ON for 5 Seconds (during this Outlet valve should be OFF).

    After 5 seconds when the stirrer has switched OFF, if High Level is ON, Start Outlet Valve till Low level is reached.

    When Low level is reached, stop Outlet Valve and again start inlet valve and repeat the process.

    a level transmitter is used for sensing level,
    If it reads value <=15.0 then it’s a Low Level & If it reads value >=85.0 it is a High Level.

    write logic for varying the tank level.

  4. Which ultrasonic sensor should I use with PLC to detect water level.


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